Powershift gears, in the form of, for example, an uninterruptible gearbox, have already become known along with the previously known manual gearboxes, for instance, for passenger cars, where the speed is changed or where the gearshift process is performed by the vehicle's driver by actuating a gearshift lever as well as automatic gearshifts in the form of planetary gears. Such a powershift gearbox displays a start element in the form of a friction clutch and has a second friction clutch by means of which it is possible, when the starting clutch is depressed and when a torque acts upon the primary gear shaft, to transmit the torque between the primary shaft and the output shaft of the gear so that a switching process can be brought about without any interruption in the traction force.
Gears by means of which one can perform power shifts have already also become known under the term of the “double-clutch gear.” Such a double-clutch gear can be construed as two series-nested automated gears, where gear pairs as well as a friction clutch are associated with each gear input shaft by means of synchronized claw clutches or clutches.
The gears or gear steps of such a double-clutch gear can be connected by at least one gear actuator and the clutches can be connected by, for example, one clutch actuator each.
In a routine driving mode, the drive moment of the combustion engine is transmitted via one of the two clutches, the pertinent primary gear shaft as well as a gear step that is associated with the particular primary gear shaft to the differential, and from the latter, it is further passed on to the wheels.
When a gear-shifting process is to take place and when the vehicle is in the normal driving mode, then the friction clutch, associated with the engaged gear step, is closed and the other friction clutch is opened and the pertinent target gear step can be engaged. By depressing the new friction clutch associated with the target gear step, said new friction clutch determines the flow of moments via the new target gear step and thus also the flow of moments via the old gear step that is still engaged. The new friction clutch here is first of all in a state of slippage that later on changes into stiction, or static friction, state. After the new target gear step or the new friction clutch has completely taken over the moment, the friction clutch, associated with the old gear step, is released and, as a result, the corresponding gear part is uncoupled from the moment transmission. After a synchronization process between the engine revolution number and the gear revolution number, the vehicle then runs in the new target gear step and the friction clutch, associated with the latter, will no longer slip.
A so-called overlap gearshift was described above, where, however, as a result of inexact overlaps, there can be moment jolts, something that in the final analysis can be illustrated as an acceleration change when the gear is shifted.